Transformation of Aromatic Ether- and Amine-Containing Pharmaceuticals during Chlorine Disinfection

Abstract

Many of the human pharmaceuticals detected in municipal wastewater effluent, surface water, and groundwater contain functional groups that could undergo transformation reactions during chlorine disinfection. To assess the potential importance of these reactions to the environmental fate of pharmaceuticals, the rate of transformation of a group of compounds was measured over a pH range of 5-10. Several of the pharmaceuticals reacted rapidly with free chlorine (i.e., HOCl/OCl-) and would be expected to undergo transformation under the conditions typically encountered in many chlorine disinfection systems. For compounds containing aromatic ether functional groups, the rate of transformation was strongly affected bythe other substituents on the ring. The amine-containing pharmaceuticals underwent a rapid reaction with hypochlorous acid to form chlorinated amines, which could be converted back into the parent compound by reaction with thiosulfate. In the absence of thiosulfate, the chlorinated amines slowly decomposed to form species that could not be converted back into the parent compound. The reaction rates of the pharmaceuticals with combined chlorine (i.e., chloramines) were significantly slower, and transformation of the compounds would not be expected under the conditions encountered during chloramination.

Chlorination of lignin by ubiquitous fungi has a likely role in global organochlorine production

“…Our detection of only 5-chlorovanillin in the samples likely indicates selective chlorination of phenolic guaiacyl units because the aromatic hydroxyl group in these structures activates the adjacent 5-position toward electrophilic attack (31). This result is unsurprising; even though the frequency of phenolic units in lignin is only on the order of 10-20% (32), the rate constant for addition of HOCl to a phenol is several hundredfold higher than for addition to a methoxybenzene at pH 6.5, the acidity of our cultures (17,18).…”

“…It remains to be seen whether fungal CPOs are expressed in lignocellulose or chlorinate it in vivo, but the hypothesis is attractive because the mycelial growth habit of lignocellulolytic fungi places secreted enzymes in very close contact with targeted plant cell wall polymers. Because HOCl is too reactive to diffuse over long distances (17,18), this juxtaposition would increase the likelihood that lignin is chlorinated.…”

Treatment options for wastewater effluents from pharmaceutical companies

“…By-products of acetaminophen include the toxic byproducts N-acetyl-p-benzoquinin e imine and 1,4-benzoquinone. Both metoprolol and sulfamethoxazole form carcinogens such as chloramines as one of their oxidation products and this may be due to the fact that ammonia chlorination was about one thousand times faster than phenol chlorination (Pinkston and Sedlak, 2004).…”

Base-catalyzed reactions of environmentally relevant N-chloro-piperidines. A quantum-chemical study

“…13, 49 The two main reaction paths were found to be intramolecular dehydrohalogenation and Grob fragmentation.…”